This invention relates to dispensing fluids containing dispersed or suspended particles. More particularly, it relates to methods and apparatus for dispensing a very small and precise amount of particles dispersed in a fluid in such areas as ceramics, metallics and latex spheres.
The drive toward miniaturization in the electronics industry has resulted in a need for greater precision in placement accuracy and volumetric control for dispensing adhesives and coatings. Conventional dispensing techniques use either positive displacement pumps or timed valving of fluid under pressure, but the precision of these methods is limited by the tendency of the fluids to adhere to the dispense tips and the fluid inside.
In the electronics area, a number of applications also require the dispensing of slurries of metal or ceramic particles. One of the key applications is for superconductive material printing. Another application is for latex particle-laden flows where uniform particle diameters are deposited so one may measure them later in the system or light may be scattered from them to measure velocities. In the medical field, the coating of latex particles is desired.
The conventional technology for many of the applications which the present invention replaces is that of silk screening. Silk screening has some very constraining requirements which include the requirement that the fluid must be very viscous. The time required to turn around a new screen and bring the process up and running is too long. It is generally for high volume applications.